1. Field of the Invention
The present invention relates to a composite material and a method for producing the same. The composite material of the present invention is improved in surface physical and chemical properties such as water repellency, wettability, adhesion, mechanical durability, and transparency. The composite material of the present invention is useful for water-repellent glass and surface-modified plastics such as those used in building interiors, automobiles, vehicles, aircraft, ships, optical instruments (e.g., cameras), and household and office appliances.
2. Description of the Prior Art
Heretofore, an organic silicon compound having a siloxane bond has been generally used as a water repellent for glass. In practice, a film of siloxane polymer (or silicone) is formed on a glass surface by treating the glass surface with a monomer gass of alkylhalosilane followed by hydrolysis, or by applying a solution of polydimethylsiloxane to the glass surface followed by heating and drying. The water repellent glass produced by these conventional methods are disadvantageous in that the silicone film has poor adhesion to the glass surface so that it is easily peeled off the glass in the peel test with an adhesive tape.
In addition, the above-mentioned methods involve some problems. The first method involves the generation of a harmful hydrogen halide gas and the second method causes the strength of the treated glass to decrease due to heating and requires a time-consuming step of removing solvent from the water repellent film.
There are also some problems with general-purpose plastics such as polyethylene, polystyrene, polycarbonate, and polymethyl methacrylate which are used for building interiors and vehicles owing to lightness, ease of fabrication, and low price. Specifically, many plastics are attacked by organic solvents, degraded by light, ozone, and rain, and are easily scratched due to low surface hardness. Transparent plastics which are used for optical instruments (e.g., glasses, cameras, and lenses), windows, doors, cups, and showcases suffer the same problems as well.
For the solution of these various problems, many attempts have been made to coat the surface of plastics with a fluoroplastic resin or silicone resin which is superior in chemical resistance and weather resistance. Unfortunately, the protective coatings of these resins have poor adhesion to other plastics due to their low polarity and surface wettability. Thus they are easily peeled off when subjected to a great peel force. In addition, the weak adhesion of these resins to other plastics permits water and foreign materials to enter the interface between the plastics surface and the protective coating thereon, which leads to the separation of the protective coatings.
There are methods other than those mentioned above for making protective coatings. These methods include a wet process of dipping a plastics molding in a resin solution followed by evaporation of solvent, and a dry process which employs plasma polymerization on the surface of a plastics molding. These processes, however, do not necessarily provide protective coatings having good adhesion.
The present invention provides a protective coating having good adhesion which is formed by a process different from conventional processes such as those disclosed in Japanese Patent Laid-Open Nos. 65575/1977, 7474/1979, and 147431/1983. The processes disclosed in these references are, respectively, a process for forming a protective coating from an organosilicon compound, a process for coating boron trifluoride under the protective coating to improve adhesion, and a process for making an undercoating of an aromatic compound. According to the present invention, a protective coating having good adhesion is produced in a different manner that the above-mentioned conventional methods.